Manufacture of glass containers

ABSTRACT

A method of manufacturing glass containers, e.g., glass bottles, comprises the steps of: A. FORMING THE CONTAINERS IN A FORMING MACHINE; B. IMMEDIATELY THEREAFTER, AND WHILE THEY ARE STILL HOT FROM THE FORMING, CONTACTING THE CONTAINERS WITH A METAL-ORGANIC COMPOUND IN LIQUID FORM AND OF HIGH THERMAL STABILITY SUCH THAT SUBSTANTIALLY NO DECOMPOSITION OF THE METAL-ORGANIC COMPOUND TAKES PLACE ON CONTACT; C. SUBJECTING THE CONTAINERS TREATED AS IN (B) TO A HEAT TREATMENT TO CAUSE THE METAL-ORGANIC COMPOUND TO REACT WITH THE GLASS AND FORM A DIFFUSE LAYER OF REACTION PRODUCT WITHIN THE GLASS SURFACE; AND D. TREATING THE CONTAINERS WHILE AT A TEMPERATURE OF AT LEAST 450* WITH A METAL COMPOUND IN LIQUID OR VAPOR FORM WHICH DECOMPOSES RAPIDLY ON CONTACT WITH THE CONTAINERS AT THE CONTACTING TEMPERATURE TO PRODUCE A SURFACE FILM OF METAL OXIDE. Tin and titanium compounds are mentioned as suitable reagents, and steps (c) and (d) may take place simultaneously.

United States Patent Budd [451 Apr. 18, 1972 [54] MANUFACTURE OF GLASSCONTAINERS Primary Examiner-Frank W. Miga An h [72] Inventor: SydneyMaurice Budd, Edgware, England omey Cus man Darby & Cushman [73]Assignee: United Glass Limited, Staines, Middlesex, ABSTRACT England Amethod of manufacturing glass containers, e.g., glass bot- [22] Filed;Man 30 970 tles, comprises the steps of:

Appl. No.: 23,996

' [52] U.S.'Cl..' ..65/30, 65/60, 65/1 1 1, 65/117, 65/119 [51] Int. Cl...C03c 15/00, C03c 17/00 [58] Field of Search ..65/60,30,111,117,119

[56] References Cited UNITED STATES PATENTS 3,498,819 3/1970 Lyle et a1...65/60 X 3,516,81 l 6/1970 Gatchet et a1. ..65/60 3,352,707 11/1967Rickard 65/60 X 3,352,708 ll/1967 Lyon et a1. ..65/60 X 3,161,53712/1964 Dettre et al.... ..65/60 X 3,420,693 1/1969 Scholes ..65/60 X3,425,859 2/1969 Steigelman ..65/60 X 3,455,722 7/1969 Kushihashi..65/60 X 3,014,815 12/1961 Lely et a1. .....65/60 X 2,809,124 10/1957Rick ..65/60 X 3,004,863 10/1961 Gray et a1. ..65/60 X a. forming thecontainers in a forming machine;

b. immediately thereafter, and while they are still hot from theforming, contacting the containers with a metal-organic compound inliquid form and of high thermal stability such that substantially nodecomposition of the metal-organic compound takes place on contact;

c. subjecting the containers treated as in (b) to a heat treatment tocause the metal-organic compound to react with the glass and form adiffuse layer of reaction product within the glass surface; and

d. treating the containers while at a temperature of at least 450 with ametal compound in liquid or vapor form which decomposes rapidly oncontact with the containers at the contacting temperature to produce asurface film of metal oxide.

Tin and titanium compounds are mentioned as suitable reagents, and steps(c) and (d) may take place simultaneously.

12 Claims, N0 Drawings 1 MANUFACTURE GLASS CONTAINERS This inventionrelates to the manufacture of glass containers, such as bottles, jars,tumblers, tableware and the like and is especially concerned with amethod of manufacturing glass containers having substantial strength.

A number of methods have been proposed hitherto for improving thestrength of glass containers. These include methods in which the glasscontainers are treated with a metal compound in liquid or vapor formimmediately after they have beenformed, andbefore they have beenannealed. In one such method the hot containers are contacted with thevapor of a metal compound which rapidly decomposes on contact withthe'hot glass to. produce a metal oxide film on the glass. This metaloxidefilm serves to protect the glass, after it has been cooled, fromscratching and abrasion, and thereby prevents the loss of strength whichwould otherwise occur in an untreated bottle subjected toscratching andabrasion. Although treating a container in this way does not make itstronger at the point of manufacture, it does make it stronger inservice, since it prevents, to a substantial extent, the containerlosing in use its original strength.

In another known method glass containers are contacted, immediatelyafter formation, with a liquid metal-organic compound. They are thenpassed into the annealing lehr wherein decomposition and reactionbetween the metal-organic compound and the glass surface occurs, givingrise to'a diffused layer of reaction product in theglass surface. Aglass container manufactured in this way has'increased strength at thepoint of manufacture.

In another method of improving the strength of a glass con.- tainer,which is a refinement of thelast-mentioned method, the liquidmetal-organic compound is one which partially decomposes on contact withthe hot glass to produce a metal compound which reacts. rapidly withthehot glassto provide a metal oxide film, while the remainder reactsslowly with the glass while the glass is being annealed to produce adiffused layer of reaction product within the glass surface.

Itis the object of the present invention toprovide a method ofmanufacturing glass, containers which are substantially stronger at thepoint of manufacture than are glass. containers manufactured hitherto,both by conventional method and by methods involving intermediatetreatment operations such as those outlinedabove.

According to the invention a method of manufacturing glass containerscomprises the steps of:

a. forming the containersin a forming-machine;

b. immediately thereafter, and whi'le'they are still hot from theforming, contacting the containers with a metal-or.- ganic compound inliquid form and of high thermal stability such that substantially nodecomposition of the metal-organic compoundtakes place on contact;

c. subjecting the containers treatedas in (b) to a heat treatment tocause the metal-organic compound to react with the glass and form adiffuse layer of reaction product within the glass surface; and

450C with a metal compound in liquid or vapor form which decomposesrapidly on contact withthe containers at the contacting temperature toproduce a surface film of metal oxide.

The glass containers may subsequently be further treated, while at atemperature of 80 180C, with an aqueous solution or emulsion of apolyoxyethylene glycol, a derivative thereof, or polyethylene. We havefound that by means of this method glass containers may be producedwhich are substantially stronger than containers manufactured inaccordance with the prior methods discussed above.

In essence the method of the invention may comprise three distinctstages following the initial forming step (a). 1n the first stage, step(b), the formed glass containers are treated with a metal-organiccompound after which they are heat-treated in the second stage, so as toproduce a diffuse layer of reaction product within the glass surface.Clearly, it is necessary to use treating the containers while at atemperature of at least for this purpose a metal compound which willpermit such reaction to occur, and we have found that certain compoundsof tin or titanium are suitable for this purpose. These materials,dissolved in a suitable solvent, are suitably applied to the glasscontainers immediately after they leave the forming machine. Preferablythe containers are transferred to a conveyor over a part of which ismounted a tunnel provided with a spray or sprays to which a constantsupply of liquid material is pumped. Preferably at least two sprays areused, the flow rate through each spray being in the range 2 12 mls perminute.

After passing through the application tunnel it is necessary, as thesecond stage, to heat-treat the containers to ensure maximum reaction ofthe applied metal-organic material with the glass, so as to obtainadiffuse layer. In practice this may be accomplished by passing thecontainers from the conveyor into an annealing lehr or other annealingenclosure where the hot spot temperature, i.e. the temperature at thehot end, is at least 20C higher than the annealing point of the glass.For most container glasses a hot spot temperature of 575C is suitable.

A suitable metal-organic compound of high thermal stability for use inthe first stage of the method is a material prepared by reacting a tintetrahalide, e.g. tin tetrachloride, with a lower alcohol, e.g.isopropanol, such that at no time during the reaction is the proportionof tin tetrahalide to alcohol greater than 33 percent w/w. The finalmaterial may contain between 1 and 10 percent by weight of tin, andpreferably will contain about 4 percent w/w of tin. Another suitablematerial is prepared by reacting titanium tetrachloride with a loweralkoxide of titanium, e.g. titanium tetrabutoxide, in alcohol solutionsuch that the titanium represents between 1 and 10 percent by weight ofthe solution.

In the third stage of the method according to this invention, i.e. Step(d'), the glass container surface is provided, additionally to thediffuse layer provided by the first and second stages, with a metaloxide non-diffuse layer. This is accomplished by treating the glasswhile it is at a temperature above 450C with a metal compound whichreacts with the hot glass to give a metal oxide film. Suitable materialsfor this purpose include tin chloride vapor ortitanium tetrachloride.Application of the third stage material to the glass containers may bemade by passing vapor of the material into the annealing lehr at a pointwhere the temperature of the containers is not less than 450C. In such acase, it will be appreciated that the second and third stages of thevmethod, i.e. steps (c) and (d), take place simultaneously.

The conditions of application of the third stage material will normallydepend upon the material used and on the temperature at which it isapplied. Such conditions should ensure that the final annealed, cooledcontainer is not unduly iridescent, but possesses a surface which cannotreadily be abraded by contact with a similarly treated surface. Forexample the annealing lehr may be equipped with sprays similar to thosesuggested for the first stage, to which is pumped sufficient material tocreate a mist or atmosphere of the material in a particular section ofthe lehr. The containers will be contacted with the material as theypass through this section of the lehr, and the material, upon reactionwith the hot glass, will produce a metal oxide coating on the surfacesof the containers.

Preferably, when the containers have cooled to a temperature in therange 180C, a further treatment is applied, and this consists in theapplication to the annealed containers of a film of a polyoxyethyleneglycol of high molecular weight or a monocarboxylic acid ester of such apolyethylene glycol, or of-polyethylene. The material is suitablyapplied by spraying the containers with a solution or dispersion of theorganic compound in water, and preferably is applied to the glasscontainers while they are at a temperature within the range C. Suitablematerials for this final treatment include polyethylene glycol marketedby Union Carbide Co. under the names Carbowax 1500, Carbowax 4000,'andCarbowax 6000, a polyethylene glycol mono-stearate marketed by AtlasChemicals under the name MYRJ 51/8, and polyethylene emulsions marketedby Owens Illinois Inc. under the name Duracote and by Valchem Ltd. underthe name Valsof.

The following Examples are given for the purpose of illustrating theinvention. Example 1 Glass bottles of oval shape were manufactured on aforming machine and passed on a conveyor through a hood wherein weresituated two spray heads, one on either side of the conveyor. Thebottles were subjected to treatment using a liquid prepared by reactingtin chloride with isopropyl alcohol, the final product containing 4percent w/w of tin, the flow rate through each spray being mls. perminute. After emerging from the hood the bottles were passed into anannealing lehr wherein was maintained an atmosphere containing stannicchloride vapor.

After annealing the bottles were clear and free from surface film orirridescence. Bursting pressure tests gave a mean of I32 p.s.i.,compared with 48 p.s.i. obtained on untreated bottles, 90 p.s.i. onbottles treated in the hood but not in the annealing lehr, and 70 p.s.i.on bottles treated in the annealing lehr but not in the hood.

Example 2 Cylindrical bottles were manufactured and treated as describedin Example 1, except that after annealing they were treated with a 0.1percent aqueous solution of polyethylene glycol of molecular weightapproximately 4000. This latter treatment was carried out using a singletravelling spray head situated above the bottles, and the flow rate andspeed were set such as to provide a coating on the bottles containingbetween 1 and 5 ,ug polyethylene glycol per cm of glass surface.

The bottles so obtained were given a standard abrasion by causing twolike treated bottles to be scratched together under a force of 50 lbsweight. The scratched bottles were then impacted such that on increasingthe impact level fracture occurred originating at a point through whichthe scratch passed. The treated bottles withstood a mean impact velocityof 64 inches per second, compared with 45 inches per second foruntreated bottles, 53 inches per second for bottles treated in the hoodbut not in the annealing lehr, and 47 inches per second for bottlestreated in the annealing lehr but not in the hood.

What we claim is:

l. A method of manufacturing glass containers comprising the steps of:

a. forming the glass containers in a forming machine;

b. immediately thereafter, and while the glass containers are still hotfrom the forming step, contacting the glass containers with ametal-organic compound in liquid form and of high thermal stability suchthat substantially no decomposition of the metal-organic compound takesplace on contact with the hot glass containers, said metal-organiccompound selected from tin and titanium compounds prepared by reacting atin tetrahalide with a lower alcohol or by reacting titaniumtetrachloride with a lower alkoxide of titanium;

c. subjecting the containers treated as in (b) to a heat treatment toreact the metal-organic compound with the surface of the glass and forma diffuse layer of reaction product within the glass surface, thetemperature during the heat treatment being at least 20C higher than theannealing temperature of the glass; and

d. treating the containers while at a temperature of at least 450C witha metal compound, in liquid or vapor form, which decomposes rapidly oncontact with the containers to produce a surface film of metal oxide,said metal compound being selected from the group consisting of tinchloride and titanium tetrachloride.

2. A method as claimed in claim 1 wherein the heat treatment recited instep (c) is an annealing treatment.

3. A method as claimed in claim 1 wherein steps (0) and (d) take placesimultaneously. l

4. A method as claimed in claim 1 wherein the metal-organic compound isprepared by reacting tin tetrachloride with a lower alcohol.

5. A method as claimed in claim 4 wherein the metal-organic compound isprepared by reacting tin tetrachloride with isopropanol such that at notime during the reaction is the proportion of tin tetrachloride toisopropanol greater than 33 percent by weight.

6. A method as claimed in claim 1 wherein the metal-organic compound isprepared by reacting titanium tetrachloride with a lower alkoxide oftitanium.

7. A method as claimed in claim 6 wherein titanium tetrachloride isreacted with titanium tetra-butoxide in alcoholic solution, the solutioncontaining from 1 to 10 percent by weight of the metal-organic compoundmeasured as titanium.

8. A method as claimed in claim 1 in which the metal compound of step(d) is tin chloride in vapour form.

9. A method as claimed in claim 1 wherein the containers are cooled to atemperature within the range l 80C after step (d) and then are furthertreated with polyethylene glycol, a derivative of polyethylene glycol, apolyoxyethylene glycol, a derivative of polyoxyethylene glycol, orpolyethylene.

10. A method as claimed in claim 9 wherein the additional treatment iscarried out when the containers are at a temperature between and C.

11. A method as claimed in claim 9 wherein the additional treatmentcomprises spraying the containers with a solution or emulsion of apolyethylene glycol mono-stearate.

12. A method of manufacturing glass containers comprising (a) formingthe containers in a forming machine, (b) immediately thereafter, andwhile the glass containers are still hot from forming, (c) contactingthe hot glass containers with a metal-organic compound in liquid formselected from tin and titanium compounds prepared by reacting a tintitrahalide with a lower alcohol or by reacting titanium tetrachloridewith a lower alkoxide of titanium, (d) annealing the thus treatedcontainers, and during annealing,'and while the containers are at atemperature of at least 450C, (e) contacting the containers with a metalcompound, in liquid or vapor form, selected from the group consisting oftin chloride and titanium tetrachloride.

2. A method as claimed in claim 1 wherein the heat treatment recited instep (c) is an annealing treatment.
 3. A method as claimed in claim 1wherein steps (c) and (d) take place simultaneously.
 4. A method asclaimed in claim 1 wherein the metal-organic compound is prepared byreacting tin tetrachloride with a lower alcohol.
 5. A method as claimedin claim 4 wherein the metal-organic compound is prepared by reactingtin tetrachloride with isopropanol such that at no time during thereaction is the proportion of tin tetrachloride to isopropanol greaterthan 33 percent by weight.
 6. A method as claimed in claim 1 wherein themetal-organic compound is prepared by reacting titanium tetrachloridewith a lower alkoxide of titanium.
 7. A method as claimed in claim 6wherein titanium tetrachloride is reacted with titanium tetra-butoxidein alcoholic solution, the solution containing from 1 to 10 percent byweight of the metal-organic compound measured as titanium.
 8. A methodas claimed in claim 1 in which the metal compound of step (d) is tinchloride in vapour form.
 9. A method as claimed in claim 1 wherein thecontainers are cooled to a temperature within the range 80*-180*C afterstep (d) and then are further treated with polyethylene glycol, aderivative of polyethylene glycol, a polyoxyethylene glycol, aderivative of polyoxyethylene glycol, or polyethylene.
 10. A method asclaimed in claim 9 wherein the additional treatment is carried out whenthe containers are at a temperature between 100* and 150*C.
 11. A methodas claimed in claim 9 wherein the additional treatment comprisesspraying the containers with a solution or emulsion of a polyethyleneglycol mono-stearate.
 12. A method of manufacturing glass containerscomprising (a) forming thE containers in a forming machine, (b)immediately thereafter, and while the glass containers are still hotfrom forming, (c) contacting the hot glass containers with ametal-organic compound in liquid form selected from tin and titaniumcompounds prepared by reacting a tin titrahalide with a lower alcohol orby reacting titanium tetrachloride with a lower alkoxide of titanium,(d) annealing the thus treated containers, and during annealing, andwhile the containers are at a temperature of at least 450*C, (e)contacting the containers with a metal compound, in liquid or vaporform, selected from the group consisting of tin chloride and titaniumtetrachloride.